Instagram lets people apply filters to photos they snap with their mobile devices. Some of these make the photos look as if they've been taken in the 1970s or on Polaroid cameras.

Facebook says it will keep Instagram running independently. Users will still be able to run it on rival social networks such as Twitter. That's a departure from Facebook's tendency to buy small startups and integrate the technology - or shut it down altogether.

The payment will be in cash and Facebook stock. Facebook is expected to complete its initial public offering of stock next month. The deal is expected to close by the end of June.